Why 'Disable debugWIRE and Close' after a debug session ?

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FredCailloux
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Posted by FredCailloux: Fri. Dec 24, 2021 - 03:10 PM
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Just got my newly arrived Xplained board and aeger to learn Debugging the proper way.

Soon got into trouble  after my first debug attempt.

Once I 'Stop Debugging' I could no longer re-program the ATmega328P from the Xplained board.

I was getting an error message:

A quick search on this Forum lead me to This Comment proposing to click 'Disable debugWIRE and Close'.

It worked perfectly. I am now able to re-upload a new version of my program.

So, I am wondering if this is a bug of Studio7 or Xplained board or if this is a normal behavior ?

Why would Studio7 still offer to simply 'Stop Debugging' if it is surely lead to a subsequent error on the next programming attempt. 

What would be the benefit of such behavior from the system ?

Am I doing the steps correctly ? Is there another way of going from Debugging to Programming so that this error doesn't happen ?

( Some reading suggestions welcome )

This topic has a solution.

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Tools, Evaluation and Development Kits (AVR-related), solved
Last Edited: Tue. Jan 25, 2022 - 09:53 PM
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kabasan
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Posted by kabasan: Fri. Dec 24, 2021 - 03:29 PM
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If it's your recommended behavior, more people will be in trouble.
> The target power must be turned off and then on again after each debug run.
> Cannot attach with the debugger while retaining the buggy state on the device.

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FredCailloux
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Posted by FredCailloux: Fri. Dec 24, 2021 - 03:56 PM
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Thanks for your quick reply,

Just a little more details pls. When, exactly, should the power be turned OFF ?

I go OFF while in debug mode ? or after 'Stop Debugging' is selected ?

 

And what do you mean by 

kabasan wrote:
Cannot attach with the debugger while retaining the buggy state on the device.

 

By the way

kabasan wrote:
If it's your recommended behavior, more people will be in trouble.

I am not pretending to recommend anything, I was just presenting what I did to get out of the error. Just saying.

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mike32217
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Posted by mike32217: Fri. Dec 24, 2021 - 04:13 PM
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You'll find, the hard way that if you don't do a 'Disable debugWIRE and Close' you'll BRICK the device.  Makes a decent doorstop though!

 

When you debug it sets a fuse and when you 'Disable debugWIRE and Close' it resets the fuse.

Happy Trails,

Mike

JaxCoder.com

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Gold Markclawson
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Posted by clawson: Fri. Dec 24, 2021 - 04:15 PM
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When debugging and you want to stop (and leave chip in non DWEN state) use the option on the debug menu and do what the messages tell you EXACTLY. 

 

But given that debugging starts by it downloading the code anyway do you even need to switch it out of DWEN mode anyway?

 

When you trade up to larger AVR (40 pin or more) they have more sensible and easier to operate debug interfaces (principally JTAG) so you don't have to play the debugWire song and dance all the time 

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Bronze Markdavid.prentice
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Posted by david.prentice: Fri. Dec 24, 2021 - 05:10 PM
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General rules:

 

1.  follow AS7.0 advice exactly for enabling debugWIRE.   i.e. remove power when it tells you.

 

2.  just use Debug->Start Debugging and Break.   and  Debug->Stop Debugging during development.

 

3.  when your project has finished or you go on holiday,  remember to Debug->Disable and Close.

 

(3) is wise if your memory is not very good.  Especially if you can't remember what you had for Breakfast.

 

David.

Last Edited: Fri. Dec 24, 2021 - 05:11 PM
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Bronze Markawneil
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Posted by awneil: Fri. Dec 24, 2021 - 05:14 PM
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clawson wrote:
do you even need to switch it out of DWEN mode anyway?

No, you don't.

 

You can leave it in debug mode - only switch out of DWEN when you have a specific reason to do so; eg, you've finished developing, or you want to test low-power modes.

 

FredCailloux wrote:

I was getting an error message:

 

 

You're trying to program via ISP when the chip is in debugWIRE mode (DWEN).

 

The chip can be programmed either via ISP or via debugWIRE.

 

While you're in the download - debug - fix code - download again - debug some more cycle, leave it in debugWIRE mode.

 

 

Top Tips:

  1. How to properly post source code - see: https://www.avrfreaks.net/comment... - also how to properly include images/pictures
  2. "Garbage" characters on a serial terminal are (almost?) invariably due to wrong baud rate - see: https://learn.sparkfun.com/tutorials/serial-communication
  3. Wrong baud rate is usually due to not running at the speed you thought; check by blinking a LED to see if you get the speed you expected
  4. Difference between a crystal, and a crystal oscillator: https://www.avrfreaks.net/comment...
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  6. Beginner's "Getting Started" tips: https://www.avrfreaks.net/comment...
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Bronze Markawneil
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Posted by awneil: Fri. Dec 24, 2021 - 05:17 PM (Reply to #3)
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FredCailloux wrote:
When, exactly, should the power be turned OFF ?

Microchip Studio tells you when the target needs to be power-cycled - be sure to read the messages carefully, and follow the instructions precisely.

Top Tips:

  1. How to properly post source code - see: https://www.avrfreaks.net/comment... - also how to properly include images/pictures
  2. "Garbage" characters on a serial terminal are (almost?) invariably due to wrong baud rate - see: https://learn.sparkfun.com/tutorials/serial-communication
  3. Wrong baud rate is usually due to not running at the speed you thought; check by blinking a LED to see if you get the speed you expected
  4. Difference between a crystal, and a crystal oscillator: https://www.avrfreaks.net/comment...
  5. When your question is resolved, mark the solution: https://www.avrfreaks.net/comment...
  6. Beginner's "Getting Started" tips: https://www.avrfreaks.net/comment...
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allano
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Posted by allano: Fri. Dec 24, 2021 - 08:45 PM
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Debug Wire State Diagram may help with your understandingDebugWire state diagram

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ka7ehk
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Posted by ka7ehk: Fri. Dec 24, 2021 - 10:03 PM
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My strategy is to do the following:

 

1. When a chip is new or has been ISP programmed, and a new development session is begun, enable DebugWire.

 

2. During development, even though debug is closed, leave DebugWire enabled.

 

3. ONLY when you need to go back to ISP programming, do "Disable DebugWire and Close"

 

 

 

Until Black Lives Matter, we do not have "All Lives Matter"!

 

 

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ki0bk
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This reply has been marked as the solution. 
Posted by ki0bk: Mon. Dec 27, 2021 - 09:10 PM
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The DW mode uses the reset pin for it's comm with the OCD inside the chip, so once it's enabled, the pin is no longer the reset pin!

Since ISP programming requires reset, it can't happen while in debug mode! 

If you forget your chip is in debug mode, and you later try and fail at ISP programming, just enter a debug session and then exit properly, now the ISP will work again, and no, the chip is not bricked!

It will become second nature to you after a short time, enjoy your debug sessions!

Happy New Year!

Jim

 

 

FF = PI > S.E.T

 

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grohote
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Posted by grohote: Mon. Dec 27, 2021 - 09:58 PM
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ka7ehk wrote:
My strategy is to do the following

 

Exactly, I am doing the same with JTAGICE mkII.

No need to terminate DW, in some projects may remain forever.

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Bronze Markawneil
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Posted by awneil: Mon. Dec 27, 2021 - 11:11 PM (Reply to #11)
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ki0bk wrote:
If you forget your chip is in debug mode, and you later try and fail at ISP programming, just enter a debug session and then exit properly,

IIRC, Microchip Studio will actually prompt you to do that ?

Top Tips:

  1. How to properly post source code - see: https://www.avrfreaks.net/comment... - also how to properly include images/pictures
  2. "Garbage" characters on a serial terminal are (almost?) invariably due to wrong baud rate - see: https://learn.sparkfun.com/tutorials/serial-communication
  3. Wrong baud rate is usually due to not running at the speed you thought; check by blinking a LED to see if you get the speed you expected
  4. Difference between a crystal, and a crystal oscillator: https://www.avrfreaks.net/comment...
  5. When your question is resolved, mark the solution: https://www.avrfreaks.net/comment...
  6. Beginner's "Getting Started" tips: https://www.avrfreaks.net/comment...
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